13 air or 13 pro retina (certain specifications and needs)

macrumors newbie

Hi, I want to buy a macbook, and I am not sure whether to buy rmbp 13 or air.
my use will be web browsing, word documents/powerpoint, downloading lectures from the internet, iTunes library, as well as a few other apps.
I will either buy 8gb ram, 256 gb ssd air.
or 8 gb ram 128 gb ssd pro.
I want the processor to be fast enough to last 3-4 years, without being slow (in 2-3 years). So is the air processor good now and future wise? Or should I go for the smaller ssd, but better processor in the rmbp 13. Before u say get 15 retina, I am not considering the 15 inch retina at all
Thanks

MacRumors attracts a broad audience
of both consumers and professionals interested in
the latest technologies and products. We also boast an active community focused on
purchasing decisions and technical aspects of the iPhone, iPod, iPad, and Mac platforms.